Cooling system for rotary electric machine

ABSTRACT

A cooling system includes a rotary electric machine, a pump that pumps coolant, a first coolant flow path that guides coolant to the rotary electric machine, a second coolant flow path branching off from the first coolant flow path, a pressure regulation valve provided in the second coolant flow path, a first orifice provided at downstream than the pressure regulation valve in the second coolant flow path in coolant flow direction, a third coolant flow path branching off from between the pressure regulation valve and the first orifice in the second coolant flow path and joining to a downstream than the branching position of the second coolant flow path in the first coolant flow path in coolant flow direction, and a switching valve provided in the third coolant flow path and that allows coolant flow to the first coolant flow path when experiencing a pressure of a threshold or more.

CROSS-REFERENCE TO RELATED APPLICATION

Priority is claimed on Japanese Patent Application No. 2018-046949,filed Mar. 14, 2018, the content of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a cooling system for a rotary electricmachine.

Description of Related Art

In a rotary electric machine mounted on a hybrid automobile, an electricautomobile, or the like, a magnetic field is formed on a stator core bysupplying current to a coil, and a magnetic attractive force orrepulsive force is generated between a magnet of a rotor and the statorcore. Accordingly, the rotor rotates with respect to the stator.

Incidentally, in this rotary electric machine, since iron loss isincreased in a high rotational speed state, a rotor core, a stator core,or the like, tends to easily generate heat. In the rotary electricmachine, when heat is generated according to driving, this may lead to adecrease in performance Here, various configurations for cooling arotary electric machine have been studied.

For example, Japanese Unexamined Patent Application, First PublicationNo. 2006-187105 discloses a structure in which a cooling water channelis provided in a circumferential portion of a motor case, which is anouter shell of an electric motor, and a cooling oil channel is providedin a circumferential portion of the motor case except the portion inwhich the cooling water channel is provided. In Japanese UnexaminedPatent Application, First Publication No. 2006-187105, a flow rate ofthe cooling water channel and a flow rate of the cooling oil channel arecontrolled according to a temperature of the coil wound on a motorstator.

Meanwhile, a structure (hereinafter, referred to as “a structure in therelated art”) including a rotary electric machine, a pump configured topump a coolant, a coolant flow path extending from the pump to therotary electric machine and configured to guide the coolant, and anorifice provided in the coolant flow path is known. In the structure inthe related art, cooling/lubrication is performed at a constant flowrate from a low rotational speed state (a low vehicle speed) to a highrotational speed state (a high vehicle speed).

SUMMARY OF THE INVENTION

However, since a flow rate is not increased at a high vehicle speed inthe structure in the related art, a flow rate of a coolant (hereinafter,referred to as “a cooling flow rate”) for cooling a rotary electricmachine is not optimized according to a vehicle speed. For example, whena corresponding cooling flow rate is set for a high vehicle speed,cooling/lubrication may be excessively performed at a low vehicle speed(a regular low vehicle speed), and this may lead to deterioration indriving loss due to an increase in size of a pump or deterioration inmovement friction of a power transmission mechanism.

An aspect of the present invention is directed to providing a coolingsystem for a rotary electric machine capable of optimizing a coolingflow rate according to a vehicle speed.

(1) A cooling system for a rotary electric machine according to anaspect of the present invention includes a rotary electric machine; apump configured to increase and decrease a flow rate of a coolantaccording to a magnitude of a rotational speed of the rotary electricmachine and pump the coolant; a first coolant flow path extending fromthe pump to the rotary electric machine and configured to guide thecoolant to the rotary electric machine; a second coolant flow pathbranching off from the first coolant flow path and configured to guidethe coolant to the pump; a pressure regulation part provided in thefirst coolant flow path and configured to regulate a pressure in thefirst coolant flow path; a flow rate regulation part provided at aposition downstream than the pressure regulation part in the secondcoolant flow path in a flow direction of the coolant and configured toregulate a flow rate of the coolant; a third coolant flow path branchingoff from a position between the pressure regulation part and the flowrate regulation part in the second coolant flow path and joining to aposition downstream than a branching position of the second coolant flowpath in the first coolant flow path in the flow direction of thecoolant; and a flow path switching part provided in the third coolantflow path and configured to allow a flow of the coolant to the firstcoolant flow path when experiencing a pressure of a threshold or more.

(2) In the aspect of the present invention, the cooling system for arotary electric machine may further include a mechanism sectionmechanically connectable to the rotary electric machine; a fourthcoolant flow path branching off from the first coolant flow path andconfigured to guide the coolant to the mechanism section; and a secondflow rate regulation part provided in the fourth coolant flow path andconfigured to regulate a flow rate of the coolant.

(3) In the aspect of the present invention, the branching position ofthe fourth coolant flow path may be provided between the branchingposition of the second coolant flow path and a joining position of thethird coolant flow path joining with the first coolant flow path.

(4) In the aspect of the present invention, the cooling system for arotary electric machine may further include a third flow rate regulationpart provided between the joining position of the third coolant flowpath joining with the first coolant flow path and the branching positionof the fourth coolant flow path from the first coolant flow path andconfigured to regulate a flow rate of the coolant.

(5) In the aspect of the present invention, the cooling system for arotary electric machine may further include a fifth coolant flow pathbranching off from a position downstream than the third flow rateregulation part in the first coolant flow path in a flow direction ofthe coolant and configured to guide the coolant to a magnet of therotary electric machine; and a fourth flow rate regulation part providedin the fifth coolant flow path and configured to regulate a flow rate ofthe coolant.

According to the aspect of (1), since the pump configured toincrease/decrease a flow rate of the coolant according to a magnitude ofa rotational speed of the rotary electric machine and pump the coolantis provided, a cooling flow rate at a high vehicle speed can beincreased by increasing a flow rate of the coolant as a rotational speedof the rotary electric machine is increased, and cooling performance ata high vehicle speed can be improved. Meanwhile, a cooling flow rate ata low vehicle speed can be reduced by reducing a flow rate of thecoolant as a rotational speed of the rotary electric machine is reduced,and excessive cooling can be avoided from being performed. In addition,since the second coolant flow path branching off from the first coolantflow path and configured to guide the coolant to the pump is provided,some (surplus coolant) of the coolant flowing through the first coolantflow path can be circulated in the second coolant flow path. Inaddition, since the pressure regulation part provided in the firstcoolant flow path and configured to regulate a pressure in the firstcoolant flow path is provided, a flow rate of the coolant flowingthrough the first coolant flow path can be regulated. In addition, sincethe flow rate regulation part provided at a position downstream than thepressure regulation part in the second coolant flow path in the flowdirection of the coolant and configured to regulate a flow rate of thecoolant is provided, a pressure in the second coolant flow path can beincreased according to an increase in the coolant at a high vehiclespeed. In addition, since the third coolant flow path branching off froma position between the pressure regulation part and the flow rateregulation part in the second coolant flow path and joining to aposition downstream than a branching position of the second coolant flowpath in the first coolant flow path in the flow direction of the coolantis provided, some of the coolant flowing through the second coolant flowpath can flow toward the rotary electric machine through the thirdcoolant flow path and the first coolant flow path. In addition, sincethe flow path switching part provided in the third coolant flow path andconfigured to allow a flow of the coolant to the first coolant flow pathwhen experiencing a pressure of a threshold or more is provided, whenthe coolant flows from the second coolant flow path to the third coolantflow path and a pressure in the third coolant flow path becomes athreshold or more, the coolant from the second coolant flow path canflow toward the rotary electric machine through the third coolant flowpath and the first coolant flow path. Accordingly, the cooling flow ratecan be optimized according to a vehicle speed.

According to the aspect of (2), the mechanism section mechanicallyconnectable to the rotary electric machine and the fourth coolant flowpath branching off from the first coolant flow path and configured toguide the coolant to the mechanism section are provided, since some ofthe coolant flowing through the first coolant flow path can be guided tothe mechanism section through the fourth coolant flow path, themechanism section can be lubricated with the coolant. In addition, thesecond flow rate regulation part provided in the fourth coolant flowpath and configured to regulate a flow rate of the coolant is provided,since a flow rate of the coolant flowing toward the mechanism sectionthrough the fourth coolant flow path is restricted, the coolant canactively flow toward the rotary electric machine through the firstcoolant flow path. That is, the rotary electric machine can be activelycooled by prioritizing a flow of the coolant to the rotary electricmachine over the flow of the coolant to the mechanism section whilelubricating the mechanism section with the coolant.

According to the aspect of (3), since the branching position of thefourth coolant flow path is provided between the branching position ofthe second coolant flow path and a joining position of the third coolantflow path joining with the first coolant flow path, the coolant flowingtoward the rotary electric machine through the third coolant flow pathand the first coolant flow path can be prevented from flowing to themechanism section through the fourth coolant flow path.

According to the aspect of (4), since the third flow rate regulationpart provided between the joining position of the third coolant flowpath joining with the first coolant flow path and the branching positionof the fourth coolant flow path from the first coolant flow path andconfigured to regulate a flow rate of the coolant is provided, thecoolant flowing toward the rotary electric machine through the thirdcoolant flow path and the first coolant flow path can be prevented fromflowing to the mechanism section through the first coolant flow path.

According to the aspect of (5), when the fifth coolant flow pathbranching off from a position downstream than the third flow rateregulation part in the first coolant flow path in the flow direction ofthe coolant and configured to guide the coolant to the magnet of therotary electric machine and the fourth flow rate regulation partprovided in the fifth coolant flow path and configured to regulate aflow rate of the coolant are provided, since some of the coolant flowingthrough the first coolant flow path can be guided to the magnet throughthe fifth coolant flow path, the magnet can be cooled. In addition, thefourth flow rate regulation part provided in the fifth coolant flow pathand configured to regulate a flow rate of the coolant is provided, sincea flow rate of the coolant flowing toward the magnet through the fifthcoolant flow path is restricted, the coolant can actively flow towardthe rotary electric machine (for example, a coil) through the firstcoolant flow path.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration view of a cooling system for arotary electric machine according to an embodiment.

FIG. 2 is a schematic configuration view of a rotary electric machineaccording to the embodiment.

FIG. 3 is a view for explaining a flow of a coolant in a first vehiclespeed zone according to the embodiment.

FIG. 4 is a view for explaining a flow of a coolant in a second vehiclespeed zone according to the embodiment.

FIG. 5 is a view for explaining a flow of a coolant in a third vehiclespeed zone according to the embodiment.

FIG. 6 is a view for explaining an action of a cooling system accordingto the embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of the present invention will be describedwith reference to the accompanying drawings. In the embodiment, acooling system for a rotary electric machine (a traveling motor) mountedon a vehicle such as a hybrid automobile, an electric automobile, or thelike, is exemplarily described.

<Cooling System for a Rotary Electric Machine>

FIG. 1 is a schematic configuration view showing the entireconfiguration of the cooling system for a rotary electric machine(hereinafter, simply referred to as “a cooling system”) according to theembodiment.

As shown in FIG. 1, a cooling system 29 includes a rotary electricmachine 1, a pump 30, a mechanism section 55, a plurality of coolantflow paths 31 to 36, a pressure regulation valve 40 (a pressureregulation part), a plurality of orifices 41 to 46 (a flow rateregulation part), and a switching valve 50 (a flow path switching part).In FIG. 1, reference numeral 58 designates an oil pan, and referencenumeral 59 designates a strainer.

<Rotary Electric Machine>

FIG. 2 is a schematic configuration view showing the entireconfiguration of the rotary electric machine 1 according to theembodiment. FIG. 2 is a view including a cross section taken along avirtual plane including an axis C.

As shown in FIG. 2, the rotary electric machine 1 includes a case 2, astator 3, a rotor 4, an output shaft 5, and a coolant supply mechanism(not shown).

The case 2 has a cylindrical box shape configured to accommodate thestator 3 and the rotor 4. A coolant (not shown) is accommodated in thecase 2. A part of the stator 3 is disposed in the case 2 while beingsubmerged in the coolant. For example, automatic transmission fluid(ATF) or the like, which is a working oil used for lubrication, powertransmission, or the like, of a transmission, is used as the coolant.

The output shaft 5 is rotatably supported by the case 2. In FIG. 2,reference sign 6 designates a bearing that rotatably supports the outputshaft 5. Hereinafter, a direction along the axis C of the output shaft 5is referred to as “an axial direction,” a direction perpendicular to theaxis C is referred to as “a radial direction” and a direction around theaxis C is referred to as “a circumferential direction.”

The stator 3 includes a stator core 11, and a coil 12 wound on thestator core 11.

The stator core 11 is formed in a cylindrical shape disposed coaxiallywith the axis C. The stator core 11 is fixed to an inner circumferentialsurface of the case 2. For example, stator core 11 is configured bylaminating electromagnetic steel plates in the axial direction. Further,the stator core 11 may be a so-called pressed powder core obtained bypressing magnetic metal powder.

The coil 12 is wound on the stator core 11. The coil 12 includes a Uphase coil, a V phase coil and a W phase coil, which are disposed tohave a phase difference of 120° from each other in the circumferentialdirection. The coil 12 includes an insertion section 12 a inserted intoa slot (not shown) of the stator core 11, and a coil end portion 12 bprotruding from the stator core 11 in the axial direction. A magneticfield is generated in the stator core 11 by flowing current to the coil12. In FIG. 2, reference sign 12 b 1 designates a first coil endportion, and reference sign 12 b 2 designates a second coil end portiondisposed at a side opposite to the first coil end portion 12 b 1 in theaxial direction.

The rotor 4 is disposed inside the stator 3 in the radial direction atan interval therefrom. The rotor 4 is fixed to the output shaft 5. Therotor 4 is configured to be rotatable integrally with the output shaft 5around the axis C. The rotor 4 includes a rotor core 21, magnets 22 andend plates 23. In the embodiment, the magnets 22 are permanent magnets.

The rotor core 21 is formed in a cylindrical shape disposed coaxiallywith the axis C. The output shaft 5 is press-fitted and fixed into therotor core 21 in the radial direction. Like the stator core 11, therotor core 21 may be configured by laminating electromagnetic steelplates in the axial direction or may be a pressed powder core.

Magnet holding holes 25 passing through the rotor core 21 in the axialdirection are formed in an outer circumferential section of the rotorcore 21. The plurality of magnet holding holes 25 are disposed atintervals in the circumferential direction. The magnets 22 are insertedinto the magnet holding holes 25.

A flow path (a rotor inside flow path), which is not shown, passingthrough the rotor core 21 in the axial direction is formed in the innercircumferential section of the rotor core 21.

The end plates 23 are disposed at both end portions of the rotor core 21in the axial direction. The output shaft 5 is press-fitted and fixedinto the end plates 23 in the radial direction. The end plates 23 coverat least the magnet holding holes 25 in the rotor core 21 from bothsides in the axial direction. The end plates 23 abut outer end surfacesof the rotor core 21 in the axial direction.

In the embodiment, shaft center cooling is performed using a shaft flowpath (not shown) formed in the output shaft 5. A coolant such as oil issupplied to the magnets 22 through a shaft flow path and a rotor insideflow path, which are not shown.

<Pump>

The pump 30 (see FIG. 1) is a mechanical oil pump (MOP) driven by arotational driving force of the output shaft 5 of the rotary electricmachine 1. When the pump 30 is driven, oil for a coolant is dischargedfrom the pump 30. The discharged oil is supplied to the coolant flowpath. For example, a gear pump, a vane pump, or the like, is used as thepump 30. The pump 30 increases and decreases a flow rate of the coolantaccording to a magnitude of a rotational speed of the rotary electricmachine 1, and pumps the coolant. The pump 30 increases a flow rate ofthe coolant as a rotational speed of the rotary electric machine 1 isincreased. The pump 30 decreases a flow rate of the coolant as arotational speed of the rotary electric machine 1 is decreased.

<Mechanism Section>

As shown in FIG. 1, the mechanism section 55 is configured to bemechanically connectable to the rotary electric machine 1.

The mechanism section 55 is a power transmission mechanism configured totransfer a rotational power of the output shaft 5 (see FIG. 2) of therotary electric machine 1 to the pump 30. The mechanism section 55 isconstituted by various gears, bearings, and so on.

<Coolant Flow Path>

The plurality of coolant flow paths 31 to 36 are constituted by thesixth coolant flow paths 31 to 36. For example, the plurality of coolantflow paths 31 to 36 are configured by assembling a plurality ofpipelines. The six coolant flow paths 31 to 36 are a first coolant flowpath 31, a second coolant flow path 32, a third coolant flow path 33, afourth coolant flow path 34, a fifth coolant flow path 35 and a sixthcoolant flow path 36.

The first coolant flow path 31 extends from the pump 30 to the coil 12(the first coil end portion 12 b 1) of the rotary electric machine 1.The first coolant flow path 31 is formed to guide a coolant from thepump 30 to the first coil end portion 12 b 1.

The second coolant flow path 32 branches off from the first coolant flowpath 31, and extends from a branching position P1 (hereinafter, referredto as “a first branching position P1”) to the pump 30. The secondcoolant flow path 32 is formed to guide some of the coolant flowingthrough the first coolant flow path 31 to the pump 30.

The third coolant flow path 33 is branching off from the second coolantflow path 32, and joins at a position in the first coolant flow path 31downstream from the first branching position P1 in a flow direction ofthe coolant. The third coolant flow path 33 extends from a branchingposition P2 (hereinafter, referred to as “a second branching positionP2”) in the second coolant flow path 32 to a joining position Pj joiningwith the first coolant flow path 31. The third coolant flow path 33 isbranching off from a space between the pressure regulation valve 40 andthe first orifice 41 in the second coolant flow path 32. The thirdcoolant flow path 33 is formed to guide some of the coolant flowingthrough the second coolant flow path 32 toward the rotary electricmachine 1 through the first coolant flow path 31.

The fourth coolant flow path 34 is branching off from the first coolantflow path 31, and extends from a branching position P3 (hereinafter,referred to as “a third branching position P3”) to the mechanism section55. The fourth coolant flow path 34 is formed to guide some of thecoolant flowing through the first coolant flow path 31 to the mechanismsection 55. The third branching position P3 is provided between thefirst branching position P1 and the joining position Pj joining with thefirst coolant flow path 31.

The fifth coolant flow path 35 is branching off from the first coolantflow path 31, and extends from a branching position P4 (hereinafter,referred to as “a fourth branching position P4”) to the magnets 22 (seeFIG. 2) of the rotary electric machine 1. The fifth coolant flow path 35is formed to guide some of the coolant flowing through the first coolantflow path 31 toward the magnets 22. For example, the fifth coolant flowpath 35 communicates with a shaft flow path (not shown).

The fourth branching position P4 is provided downstream from the joiningposition Pj in the first coolant flow path 31 in the flow direction ofthe coolant.

The sixth coolant flow path 36 is branching off from the first coolantflow path 31, and extends from a branching position P5 (hereinafter,referred to as “a fifth branching position P5”) to the coil 12 (thesecond coil end portion 12 b 2) of the rotary electric machine 1. Thesixth coolant flow path 36 is formed to guide some of the coolantflowing through the first coolant flow path 31 to the second coil endportion 12 b 2. The fifth branching position P5 is provided at aposition between the fourth branching position P4 and the first coil endportion 12 b 1 in the first coolant flow path 31.

<Pressure Regulation Valve>

The pressure regulation valve 40 is provided in the first coolant flowpath 31. The pressure regulation valve 40 is able to regulate a pressurein the first coolant flow path 31. A flow rate of the coolant flowingthrough the first coolant flow path 31 is regulated by the pressureregulation valve 40. The pressure regulation valve 40 regulates apressure of the first coolant flow path 31 such that a flow rate of thecoolant flowing through the first coolant flow path 31 becomes constantwhen a vehicle speed is a first vehicle speed threshold or more (seeFIG. 6). The pressure regulation valve 40 is stroked by applying thepressure of the first branching position P1 to a tip (an upstream end)of the pressure regulation valve 40, and delivers some of the coolant(surplus coolant) flowing through the first coolant flow path 31 to thesecond coolant flow path 32. An arrow K1 in FIG. 1 designates adirection in which the pressure regulation valve 40 is stroked.

<Orifice>

The plurality of orifices 41 to 46 are constituted by the six orifices41 to 46. The six orifices 41 to 46 are the first orifice 41 (a flowrate regulation part), the second orifice 42 (a second flow rateregulation part), the third orifice 43 (a third flow rate regulationpart), the fourth orifice 44 (a fourth flow rate regulation part), thefifth orifice 45, and the sixth orifice 46.

The first orifice 41 is provided at a position downstream than thepressure regulation valve 40 in the second coolant flow path 32 in theflow direction of the coolant. The first orifice 41 regulates a flowrate of the coolant flowing through the second coolant flow path 32. Thefirst orifice 41 is a throttle provided between the pressure regulationvalve 40 and the pump 30 in the second coolant flow path 32.

The second orifice 42 is provided in the fourth coolant flow path 34.The second orifice 42 regulates a flow rate of the coolant flowingthrough the fourth coolant flow path 34. The second orifice 42 is athrottle provided between the third branching position P3 and themechanism section 55 in the fourth coolant flow path 34.

The third orifice 43 is provided between the joining position Pj and thethird branching position P3 in the first coolant flow path 31. The thirdorifice 43 regulates a flow rate of the coolant flowing through thefirst coolant flow path 31. The third orifice 43 is a throttle providedbetween the joining position Pj and the third branching position P3 inthe first coolant flow path 31.

The fourth orifice 44 is provided in the fifth coolant flow path 35. Thefourth orifice 44 regulates a flow rate of the coolant flowing throughthe fifth coolant flow path 35. The fourth orifice 44 is a throttleprovided between the fourth branching position P4 and a shaft flow path(not shown) in the fifth coolant flow path 35.

The fifth orifice 45 is provided at a position downstream than thefourth branching position P4 in the first coolant flow path 31 in theflow direction of the coolant. The fifth orifice 45 regulates a flowrate of the coolant flowing through the first coolant flow path 31. Thefifth orifice 45 is a throttle provided between the fourth branchingposition P4 and the first coil end portion 12 b 1 in the first coolantflow path 31.

The sixth orifice 46 is provided in the sixth coolant flow path 36. Thesixth orifice 46 regulates a flow rate of the coolant flowing throughthe sixth coolant flow path 36. The sixth orifice 46 is a throttleprovided between the fifth branching position P5 and the second coil endportion 12 b 2 in the sixth coolant flow path 36.

<Switching Valve>

The switching valve 50 is provided in the third coolant flow path 33.The switching valve 50 allows a flow of the coolant from the thirdcoolant flow path 33 to the first coolant flow path 31 when a pressureof a threshold or more is received. The switching valve 50 opens thethird coolant flow path 33 when the pressure or the threshold or more isreceived.

The switching valve 50 has a biasing member 51 such as a spring or thelike, a locking member 52 connected to the biasing member 51, and areceiving member 53 configured to receive the locking member 52. Forexample, the switching valve 50 is a check valve. The biasing member 51normally biases the locking member 52 in a direction opposite to theflow direction of the coolant (an arrow F1 direction in FIG. 1). Athrough-hole 53 h along the third coolant flow path 33 is formed in thereceiving member 53. The biasing member 51 normally biases the lockingmember 52 against the receiving member 53 to close the through-hole 53 hof the receiving member 53. The locking member 52 moves against abiasing force of the biasing member 51 in the flow direction of thecoolant and is separated from the receiving member 53 when a pressure ofa threshold or more is received. When the locking member 52 is separatedfrom the receiving member 53, the third coolant flow path 33 is openedand a flow of the coolant to the first coolant flow path 31 is allowed.

<Operation of Cooling System>

Hereinafter, an example of an operation of the cooling system 29according to the embodiment will be described.

First, the pump 30 is driven. Accordingly, a coolant (oil) stored in anoil pan 58 is discharged from the pump 30. The pump 30 is driven by arotational driving force of the output shaft 5 (see FIG. 2) of therotary electric machine 1. The pump 30 increases a flow rate of thecoolant as a rotational speed of the rotary electric machine 1 isincreased. The pump 30 increases a flow rate of the coolant as a vehiclespeed is increased.

Here, a vehicle speed zone of a first vehicle speed V1 or more and asecond vehicle speed V2 or less is referred to as a first vehicle speedzone S1 (a low vehicle speed zone), a vehicle speed zone of larger thanthe second vehicle speed V2 and a third vehicle speed V3 or less isreferred to as a second vehicle speed zone S2 (a middle vehicle speedzone), and a vehicle speed zone exceeding the third vehicle speed V3 isreferred to as a third vehicle speed zone S3 (a high vehicle speed zone)(see FIG. 6). In addition, a flow rate of a coolant in the first vehiclespeed zone S1 is referred to as a first flow rate A1, a flow rate of acoolant in the second vehicle speed zone S2 is referred to as a secondflow rate A2, and a flow rate of a coolant in the third vehicle speedzone S3 is referred to as a third flow rate A3. The flow rates A1 to A3of the coolant in the vehicle speed zones S1 to S3 have a relation ofA1<A2<A3.

Hereinafter, a flow of a coolant in the first vehicle speed zone S1 willbe described with reference to FIG. 3. In FIG. 3, a flow of a coolant inthe first vehicle speed zone S1 is represented as an arrow Q1.

In the first vehicle speed zone S1, the coolant discharged from the pump30 is supplied to the first coolant flow path 31. The coolant suppliedto the first coolant flow path 31 flows toward the rotary electricmachine 1 through the first coolant flow path 31.

Specifically, the coolant supplied to the first coolant flow path 31flows toward the first coil end portion 12 b 1 through the first coolantflow path 31. Some of the coolant flowing through the first coolant flowpath 31 flows toward the mechanism section 55 through the fourth coolantflow path 34. Some of the coolant flowing through the first coolant flowpath 31 flows toward the magnets 22 of the rotary electric machine 1through the fifth coolant flow path 35. Some of the coolant flowingthrough the first coolant flow path 31 flows toward the second coil endportion 12 b 2 of the rotary electric machine 1 through the sixthcoolant flow path 36.

The pressure regulation valve 40 regulates a pressure of the firstcoolant flow path 31 such that a flow rate of the coolant flowingthrough the first coolant flow path 31 becomes constant when the vehiclespeed reaches the second vehicle speed V2. Reference character T1 inFIG. 6 designates timing of pressure regulation by the pressureregulation valve 40.

In the first vehicle speed zone S1, since it is before pressureregulation by the pressure regulation valve 40, it is unlikely that some(surplus coolant) of the coolant flowing through the first coolant flowpath 31 flows into the second coolant flow path 32. In a flow of thecoolant in the first vehicle speed zone S1, a flow of the arrow Q1 inFIG. 3 becomes a main flow.

In the first vehicle speed zone S1, the switching valve 50 is unlikelyto experience a pressure of a threshold or more. In the first vehiclespeed zone S1, the switching valve 50 remains closed.

Hereinafter, a flow of the coolant in the second vehicle speed zone S2will be described with reference to FIG. 4. In FIG. 4, a flow of thecoolant in the second vehicle speed zone S2 is represented as an arrowQ2.

In the second vehicle speed zone S2, since it is after pressureregulation by the pressure regulation valve 40, some (surplus coolant)of the coolant flowing through the first coolant flow path 31 flows intothe second coolant flow path 32.

Specifically, the coolant flowing into the second coolant flow path 32flows toward the pump 30 through the second coolant flow path 32. Thesecond coolant flow path 32 functions as a circulation flow pathconfigured to return the surplus coolant in the first coolant flow path31 to the pump 30.

Since the first orifice 41 is provided in the second coolant flow path32, the pressure of the second coolant flow path 32 is graduallyincreased according to an increase in the coolant (surplus coolant)flowing into the second coolant flow path 32. A pressure (hereinafter,referred to as “an upstream pressure”) upstream from the switching valve50 in the third coolant flow path 33 is also gradually increasedaccording to an increase in the coolant flowing into the second coolantflow path 32.

The switching valve 50 allows a flow of the coolant into the firstcoolant flow path 31 when the vehicle speed reaches the third vehiclespeed V3. Reference character T2 in FIG. 6 designates an operationtiming of the switching valve 50. In the embodiment, when the vehiclespeed reaches the third vehicle speed V3, the first orifice 41 is setsuch that the upstream pressure is a pressure of a threshold or more inthe switching valve 50.

In the second vehicle speed zone S2, since it is before an operation ofthe switching valve 50, even when some of the coolant flowing throughthe second coolant flow path 32 flows into the third coolant flow path33, the coolant is unlikely to flow into the first coolant flow path 31.In the flow of the coolant in the second vehicle speed zone S2, flows ofthe arrows Q1 and Q2 in FIG. 4 are main flows.

In the second vehicle speed zone S2, the switching valve 50 is unlikelyto experience a pressure of a threshold or more. In the second vehiclespeed zone S2, the switching valve 50 remains closed.

Hereinafter, a flow of a coolant in the third vehicle speed zone S3 willbe described with reference to FIG. 5. In FIG. 5, a flow of a coolant inthe third vehicle speed zone S3 is represented as an arrow Q3.

In the third vehicle speed zone S3, since it is after pressureregulation of the pressure regulation valve 40 and after an operation ofthe switching valve 50, some of the coolant flowing through the secondcoolant flow path 32 flows into the first coolant flow path 31 whenflowing into the third coolant flow path 33. A flow of the coolant inthe third vehicle speed zone S3 become flows of the arrows Q1 to Q3 inFIG. 5.

Specifically, in the switching valve 50, when the locking member 52experiences a pressure of a threshold or more, the locking member 52moves in the flow direction of the coolant against the biasing force ofthe biasing member 51 and is separated from the receiving member 53.When the locking member 52 is separated from the receiving member 53,the third coolant flow path 33 is opened and a flow of the coolant tothe first coolant flow path 31 is allowed. The third coolant flow path33 functions as a bypass flow path configured to guide some of thecoolant flowing through the second coolant flow path 32 to the firstcoolant flow path 31.

<Action>

Hereinafter, an action of the cooling system 29 of the embodiment willbe described with reference to FIG. 6.

First, a comparative example will be described.

A cooling system in the comparative example does not have the secondcoolant flow path 32 (the circulation flow path) and the third coolantflow path 33 (the bypass flow path) in the embodiment. In thecomparative example, cooling/lubrication is performed at a constant flowrate from a low rotational speed state (a low vehicle speed) to a highrotational speed state (a high vehicle speed). Reference character Ax inFIG. 6 designates a cooling flow rate in the comparative example.

In the comparative example, since the flow rate is not increased at ahigh vehicle speed, the cooling flow rate is not optimized according tothe vehicle speed. For example, when the cooling flow rate is set to beon the high vehicle speed side, there is a high possibility thatexcessive cooling/lubrication will be performed at a low vehicle speed.For this reason, in the comparative example, it may lead todeterioration of driving loss due to an increase in size of the pump ordeterioration of stirring friction in a power transmission mechanism.

Next, the embodiment will be described.

In the embodiment, the second coolant flow path 32 (the circulation flowpath) and the third coolant flow path 33 (the bypass flow path) areprovided, the first orifice 41 is provided downstream than the pressureregulation valve 40 in the second coolant flow path 32 in the flowdirection of the coolant, and the switching valve 50 is provided in thethird coolant flow path 33. In the embodiment, since the third coolantflow path 33 is a bypass flow path configured to guide some of thecoolant flowing through the second coolant flow path 32 to the firstcoolant flow path 31 according to an operation of the switching valve50, the flow rate can be increased at a high vehicle speed. In FIG. 6,reference sign Ac designates a cooling flow rate in the embodiment, andreference sign At designates a lubrication flow rate.

Meanwhile, since the second coolant flow path 32 is a circulation flowpath configured to circulate some of the coolant flowing through thefirst coolant flow path 31 toward the pump 30 at a low vehicle speed, itis unlikely to perform excessive cooling/lubrication. Accordingly, inthe embodiment, it is unlikely to lead to deterioration in driving lossdue to an increase in size of the pump or deterioration in stirringfriction of the power transmission mechanism.

As described above, the cooling system 29 of the embodiment includes therotary electric machine 1, the pump 30 configured to increase anddecrease a flow rate of a coolant according to a magnitude of arotational speed of the rotary electric machine 1 and pump the coolant,the first coolant flow path 31 extending from the pump 30 to the rotaryelectric machine 1 and configured to guide the coolant to the rotaryelectric machine 1, the second coolant flow path 32 branching off fromthe first coolant flow path 31 and configured to guide the coolant tothe pump 30, the pressure regulation valve 40 provided in the firstcoolant flow path 31 and configured to regulate a pressure in the firstcoolant flow path 31, the first orifice 41 provided at a positiondownstream than the pressure regulation valve 40 in the second coolantflow path 32 in the flow direction of the coolant and configured toregulate a flow rate of the coolant, the third coolant flow path 33branching off from a position between the pressure regulation valve 40and the first orifice 41 in the second coolant flow path 32 and joiningto a position downstream than the branching position P1 of the secondcoolant flow path 32 in the first coolant flow path 31 in the flowdirection of the coolant, and the switching valve 50 provided in thethird coolant flow path 33 and configured to allow a flow of the coolantto the first coolant flow path 31 when experiencing a pressure of athreshold or more.

According to the configuration, since the pump 30 configured to increaseand decrease a flow rate of the coolant according to a magnitude of arotational speed of the rotary electric machine 1 and pump the coolantis provided, a cooling flow rate at a high vehicle speed is increased byincreasing a flow rate of the coolant as a rotational speed of therotary electric machine 1 is increased, and cooling performance at ahigh vehicle speed can be improved. Meanwhile, since the flow rate ofthe coolant is decreased as a rotational speed of the rotary electricmachine 1 is reduced, a cooling flow rate at a low vehicle speed can bereduced, and it is possible to avoid excessive cooling from beingperformed. In addition, since the second coolant flow path 32 branchingoff from the first coolant flow path 31 and configured to guide thecoolant to the pump 30 is provided, it is possible to circulate some(surplus coolant) of the coolant flowing through the first coolant flowpath 31 in the second coolant flow path 32. In addition, since thepressure regulation valve 40 provided in the first coolant flow path 31and configured to regulate the pressure in the first coolant flow path31 is provided, a flow rate of the coolant flowing through the firstcoolant flow path 31 can be regulated. In addition, since the firstorifice 41 provided at a position downstream than the pressureregulation valve 40 in the second coolant flow path 32 in the flowdirection of the coolant and configured to regulate a flow rate of thecoolant is provided, a pressure in the second coolant flow path 32 canbe increased according to an increase in the coolant at a high vehiclespeed. In addition, since the third coolant flow path 33 branching offfrom a position between the pressure regulation valve 40 and the firstorifice 41 in the second coolant flow path 32 and joining to a positiondownstream than the branching position P1 of the second coolant flowpath 32 in the first coolant flow path 31 in the flow direction of thecoolant is provided, some of the coolant flowing through the secondcoolant flow path 32 can flow toward the rotary electric machine 1through the third coolant flow path 33 and the first coolant flow path31. In addition, since the switching valve 50 provided in the thirdcoolant flow path 33 and configured to allow a flow of the coolant tothe first coolant flow path 31 when experiencing a pressure of athreshold or more is provided, when the coolant flows from the secondcoolant flow path 32 to the third coolant flow path 33 and a pressure inthe third coolant flow path 33 becomes a threshold or more, the coolantfrom the second coolant flow path 32 can flow toward the rotary electricmachine 1 through the third coolant flow path 33 and the first coolantflow path 31. Accordingly, a cooling flow rate can be optimizedaccording to a vehicle speed.

In the embodiment, since the mechanism section 55 mechanicallyconnectable to the rotary electric machine 1 and the fourth coolant flowpath 34 branching off from the first coolant flow path 31 and configuredto guide the coolant to the mechanism section 55 are provided, thefollowing effects are exhibited. Since some of the coolant flowingthrough the first coolant flow path 31 can be guided to the mechanismsection 55 through the fourth coolant flow path 34, it is possible tolubricate the mechanism section 55 with the coolant. In addition, thesecond orifice 42 provided in the fourth coolant flow path 34 andconfigured to regulate a flow rate of the coolant is provided, since aflow rate of the coolant flowing toward the mechanism section 55 throughthe fourth coolant flow path 34 is restricted, it is possible to causethe coolant to actively flow toward the rotary electric machine 1through the first coolant flow path 31. That is, the rotary electricmachine 1 can be actively cooled by prioritizing a flow of the coolantto the rotary electric machine 1 over the flow of the coolant to themechanism section 55 while lubricating the mechanism section 55 with thecoolant.

In the embodiment, since the branching position P3 of the fourth coolantflow path 34 is provided between the branching position P1 of the secondcoolant flow path 32 and the joining position Pj of the third coolantflow path 33 joining with the first coolant flow path 31, the followingeffects are exhibited. The coolant flowing toward the rotary electricmachine 1 through the third coolant flow path 33 and the first coolantflow path 31 can be prevented from flowing to the mechanism section 55through the fourth coolant flow path 34.

In the embodiment, since the third orifice 43 provided between thejoining position Pj of the third coolant flow path 33 joining with thefirst coolant flow path 31 and the branching position P3 of the fourthcoolant flow path 34 from the first coolant flow path 31 and configuredto restrict a flow rate of the coolant is provided, the followingeffects are exhibited. The coolant flowing toward the rotary electricmachine 1 through the third coolant flow path 33 and the first coolantflow path 31 can be prevented from flowing to the mechanism section 55through the first coolant flow path 31.

In the embodiment, since the fifth coolant flow path 35 branching offfrom a position downstream than the third orifice 43 in the firstcoolant flow path 31 in the flow direction of the coolant and configuredto guide the coolant to the magnets 22 of the rotary electric machine 1,and the fourth orifice 44 provided in the fifth coolant flow path 35 andconfigured to regulate a flow rate of the coolant are provided, thefollowing effects are exhibited. Since some of the coolant flowingthrough the first coolant flow path 31 can be guided to the magnets 22through the fifth coolant flow path 35, the magnets 22 can be cooled. Inaddition, the fourth orifice 44 provided in the fifth coolant flow path35 and configured to regulate a flow rate of the coolant is provided,since a flow rate of the coolant flowing toward the magnets 22 throughthe fifth coolant flow path 35 is restricted, the coolant can activelyflow toward the rotary electric machine 1 (for example, the coil 12)through the first coolant flow path 31.

While the example in which the rotary electric machine 1 is a travelingmotor mounted on a vehicle such as a hybrid automobile, an electricautomobile, or the like, has been exemplarily described in theabove-mentioned embodiment, there is no limitation thereto. For example,the rotary electric machine 1 may be a power generating motor, a motorfor another use, or a rotary electric machine (including a generator)for other than the vehicle.

While the example in which shaft center cooling is performed using theshaft flow path provided in the output shaft 5 has been exemplarilydescribed in the above-mentioned embodiment, there is no limitationthereto. For example, the coolant may be supplied to the magnets 22along a guidance wall (not shown) provided in the end plates 23 byrotation of the rotor 4. For example, the coolant may be supplied toopening sections of the end plates 23 through a supply port provided inthe case 2 or the like.

While the example in which the pump 30 is a mechanical oil pump (MOP)driven by a rotational driving force of the output shaft 5 of the rotaryelectric machine 1 has been exemplarily described in the above-mentionedembodiment, there is no limitation thereto.

For example, the pump 30 may be an electric oil pump (EOP) driven by arotational driving force of a pump motor. For example, an independentelectric motor that does not rely on a rotational driving force of theoutput shaft 5 of the rotary electric machine 1 may be used as a pumpmotor.

While the example in which cooling oil as a coolant is guided to therotary electric machine 1 has been exemplarily described in theabove-mentioned embodiment, there is no limitation thereto. For example,a water jacket may be provided in the case 2 of the rotary electricmachine 1, and cooling water serving as a coolant may be guided to awater jacket by a water pump.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the scope of the present invention. Accordingly, theinvention is not to be considered as being limited by the foregoingdescription, and is only limited by the scope of the appended claims.

What is claimed is:
 1. A cooling system for a rotary electric machinecomprising: a rotary electric machine; a pump configured to increase anddecrease a flow rate of a coolant according to a magnitude of arotational speed of the rotary electric machine and pump the coolant; afirst coolant flow path extending from the pump to the rotary electricmachine and configured to guide the coolant to the rotary electricmachine; a second coolant flow path branching off from the first coolantflow path and configured to guide the coolant to the pump; a pressureregulation part provided in the first coolant flow path and configuredto regulate a pressure in the first coolant flow path; a flow rateregulation part provided at a position downstream than the pressureregulation part in the second coolant flow path in a flow direction ofthe coolant and configured to regulate a flow rate of the coolant; athird coolant flow path branching off from a position between thepressure regulation part and the flow rate regulation part in the secondcoolant flow path and joining to a position downstream than thebranching position of the second coolant flow path in the first coolantflow path in the flow direction of the coolant; and a flow pathswitching part provided in the third coolant flow path and configured toallow a flow of the coolant to the first coolant flow path whenexperiencing a pressure of a threshold or more.
 2. The cooling systemfor a rotary electric machine according to claim 1, further comprising:a mechanism section mechanically connectable to the rotary electricmachine; a fourth coolant flow path branching off from the first coolantflow path and configured to guide the coolant to the mechanism section;and a second flow rate regulation part provided in the fourth coolantflow path and configured to regulate a flow rate of the coolant.
 3. Thecooling system for a rotary electric machine according to claim 2,wherein the branching position of the fourth coolant flow path isprovided between the branching position of the second coolant flow pathand a joining position of the third coolant flow path joining with thefirst coolant flow path.
 4. The cooling system for a rotary electricmachine according to claim 3, further comprising a third flow rateregulation part provided between the joining position of the thirdcoolant flow path joining with the first coolant flow path and thebranching position of the fourth coolant flow path from the firstcoolant flow path and configured to regulate a flow rate of the coolant.5. The cooling system for a rotary electric machine according to claim4, further comprising: a fifth coolant flow path branching off from aposition downstream than the third flow rate regulation part in thefirst coolant flow path in a flow direction of the coolant andconfigured to guide the coolant to a magnet of the rotary electricmachine; and a fourth flow rate regulation part provided in the fifthcoolant flow path and configured to regulate a flow rate of the coolant.